It is known that a cooking process, i.e., the steaming or boiling or other treatment of foodstuffs to cook them, can be accelerated and made more uniform by circulating hot air in the cooking space by a blower thereby cooking the comestible product in a uniform manner. The air is distributed by corresponding guides or baffles. In such apparatus, instead of hot or heated air, use can also be made of water vapor or steam.
The steam or steaming operation, however, can also be carried out at temperatures up to approximately 100.degree. C., at least where the interior of the oven is to be at ambient pressure.
Accordingly, when switching an apparatus, which is initially operated at a temperature of approximately 250.degree. C. by heated air for the first described cooking mode, it is generally necessary to allow the temperature to drop to approximately 100.degree. C., lest too much steam be produced and excessive pressure build-up occur.
The natural cooling of the cooking space to a temperature of 100.degree. C. for the steaming, however, takes a rather long time which can detrimentally affect the quality of the food which is to be cooked and the efficiency of the cooking operations.
Although one can open the charging door to aid somewhat in lowering the temperature, heat energy will then be lost.